Sitting at his laptop, Chris O'Ferrell types a few words into the Google search engine and up pops a link to what appears to be a military document listing suspected Taliban and al Qaeda members, date of birth, place of birth, passport numbers and national identification numbers.

Another search yields a spreadsheet of names and credit card numbers.

"All search engines will get you this," O'Ferrell said, pointing to files of spoils he has found on the Internet: Medical records, bank account numbers, students' grades, and the docking locations of 804 U.S. Navy ships, submarines and destroyers.

And it is all legal, using the world's most powerful Internet search engine.

Cybersecurity experts say an increasing number of private or putatively secret documents are online in out-of-the-way corners of computers all over the globe, leaving the government, individuals, and companies vulnerable to security breaches. At some Web sites and various message groups, techno-hobbyists are even offering instructions on how to find sensitive documents using a relatively simple search. Though it does not technically trespass, the practice is sometimes called "Google hacking."

In the decade they have been around, search engines like Google have become more powerful. At the same time, the Web has become a richer source of information as more businesses and government agencies rely on the Internet to transmit and share information. All of it is stored on computers called servers, each one linked to the Internet.

For a variety of reasons -- improperly configured servers, holes in security systems, human error -- a wide assortment of material not intended to be viewed by the public is, in fact, publicly available. Once Google or another search engine finds it, it is nearly impossible to draw back into secrecy.

That is giving rise to more activity from "Googledorks," who troll the Internet for confidential goods, security engineers said.

"As far as the number of sites affected by this, it's in the tens of thousands," said Johnny Long, 32, a researcher and developer for Computer Sciences Corp. and veteran hacker who maintains a Web site that he says keeps him connected to the hacker community. He spoke about Google hacking at the Def Con hacker convention in Las Vegas last summer, which has led to more awareness of vulnerabilities, he said.